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ACADEMIA Letters Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria Samuel Okafor Over many centuries of human existence, the spread of disease has taken turns in different dimensions and has informed different approaches in managing same (Honigsbaum, 2009; Jones & Helmreich, 2020). While level of scientific advancement informs the approaches to the out breaking diseases, political activity and passivity contributes also, to the direction and magnitude of the approach. Central to whatever effort made in reaction to the outbreak of any disease, is to protect the population involved via population immunity. While the concept of immunity itself move from individual to population immunity (Metcalf, Ferrari, Graham & Grenfell, 2015), the realization of the concept is dependent on the spreading capacity or reproductive rate of the pathogen/virus as well as the fatality rate (Prajapati & Narasimha, 2020; Harmaratne et al., 2020; Li et al., 2020). Population immunity otherwise known as herd immunity is pursued and realized through the different clinical cum pharmaceutical as well as non pharmaceutical interventions (Smith, 2010; Aschwanden, 2020; Fine, Eames & Heymann, 2011). Specifically, population/herd immunity happens when a virus can’t spread because it keeps encountering people who are protected against infection. Once a sufficient proportion of the population is no longer susceptible, any new outbreak peters out (Aschwanden, 2020; Clemente-Suárez et al, 2020). A number of scholars have argued about the plausibility of the concept of herd immunity whether by clinical cum pharmaceutical intervention or by non pharmaceutical intervention (NPI), with major focus on the operationalization and measurability of the concept with a uniform protocol across the globe as well as across the heterogeneous and homogenous populations (Jacob & Samuel, 2000; Metcalf, Ferrari, Graham & Grenfell, 2015; The Royal Society, 2020). While herd/population immunity by clinical/pharmaceutical intervention has been argued for by many scholars with substantive evidences (Prajapati & Narasimha, 2020; Academia Letters, July 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Samuel Okafor, samuel.okafor.pg76550@unn.edu.ng Citation: Okafor, S. (2021). Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria. Academia Letters, Article 2164. https://doi.org/10.20935/AL2164. 1 Harmaratne et al., 2020; Li et al., 2020; Jones & Helmreich, 2020), herd/population immunity by non pharmaceutical intervention (NPI) has been equally projected as a reality among a helpless population in certain settings (Jones & Helmreich, 2020; Metcalf, Ferrari, Graham & Grenfell, 2015). Among other approaches, natural herd immunity as part of NPI, which allowed the spread of an infection to elapse with counter infection as well as unsusceptible members of the population, has been scarcely given attention to, across generations with history of epidemic and pandemics. While some scholars see natural immunity as intellectual venture full of spurious relationships of variables and as such, with complex and complicated explanations (The Royal Society, 2020; Jacob & Samuel, 2020), other scholars view natural immunity as not plausible and as such, unworthy of intellectual attention (Aschwanden, 2020). However, research venture is an ongoing process in every discipline with discoveries, counter discoveries and advanced discoveries as the case may be in different historical epochs. As a matter of fact, the case of CoViD-19 pandemic has brought to the limelight, the natural herd immunity phenomenon in focus, as evidences from different parts of the globe have defied the argument in favour of clinical/pharmaceutical intervention in pandemic crises. For instance, a number of projections have been made concerning African nations as well as other developing nations across the globe in the absence of vaccine; however, most of these nations did not fall within the projected figures and timeframe in the absence of vaccine to curtail the pandemic. Nigeria as one of the developing nations in Africa included in the number of projections about the spread of CoViD-19 pandemic, in the absence of vaccine, did not fall into the projection figure and framework following the present realities. This can be observed in the number of cases recorded till date. Nonetheless, the southeast Nigeria with dense population both in the urban and the rural communities, and complex socioeconomic activities before, during and after CoViD-19 lockdown, did not show any sign of the pandemic as was projected from different quarters about Nigeria. CoViD-19 Pandemic First and Second Waves in Southeast Nigeria and the Question of Natural Herd Immunity Basically in the principle of herd immunity, when a pathogen invades unexposed population, there is expectation of reproduction of the infection through the index case, producing a reproduction rate (R0) of varying degrees such that, there is a possibility of either increasing the infection in the population or phasing out the presence of the pathogen from the population that is, if R0 > 1 infection spreads; if R0 ≤ 1, infection dies out (The Royal Society, 2020). While this has been viewed as possible with the help of vaccine (Metcalf, Ferrari, Graham Academia Letters, July 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Samuel Okafor, samuel.okafor.pg76550@unn.edu.ng Citation: Okafor, S. (2021). Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria. Academia Letters, Article 2164. https://doi.org/10.20935/AL2164. 2 & Grenfell, 2015; Korppi, 2018), it has been also projected as possible through non pharmaceutical interventions (NPI) (Kantner & Koprucki, 2020; WHO, 2019; Neil et al, 2020), of which in difficult experience where the scientific prowess of a generation cannot counteract the spread of a pathogen, the population were left to the mercy of the infection and counter infection by the pathogen. From the moment in history when the concept of herd immunity entered into epidemiological literature (see Topley, Wilson, 1923) to the present, the application of the NPI ie the natural herd immunity dimension of the concept has been fairly observed in some period and places in the faces of epidemics and pandemics (Flaxman et al, 2020; Liu et al, 2021). While in the past, the application of natural herd immunity has been seen in the community of scientists and researchers as the by-product of unprogressive scientific effort in mitigating the spread of a pathogen, in the present historical epoch, with the current scientific prowess of this generation, practicing natural herd immunity is more or less seen as a suicide policy especially in the case of faceless virus like CoViD-19 (Aschwanden, 2020). In the wake of current CoViD-19 pandemic, a number of nations such as United Kingdom, America, Sweden, Brazil, Nigeria, etc. have voluntarily and involuntarily applied the concept of natural herd immunity ostensibly to buy time for the development of vaccine (Aschwanden, 2020; Yanga et al, 2020; Flaxman et al., 2020). While in some of these nations, this appeared as a policy statement, in others, it was covertly observed but obtrusively visible on the rate of infections observed (Flaxman et al, 2020). In the case of Nigeria and southeast Nigeria in particular, the experience of the population from statistical revelation and scholarly observation (Okafor forthcoming) aptly demonstrated the natural herd immunity in action. The spread of novel Corona Virus Disease (COVID-19) in Nigeria has been observed as a reality since the first index case in February 2020 triggering, public policy response from the government of Nigeria (Amzat, Aminu, Kolo, Akinyele, Ogundairo & Danjibo, 2020). Currently, the spread of the virus can still be observed but rather in a very slower rate. On the 26th of March 2021, 113 new confirmed cases and 3 deaths were recorded in Nigeria. Till date, 162388 cases have been confirmed, 149986 cases have been discharged and 2039 deaths have been recorded in 36 states and the Federal Capital Territory. The 113 new cases are reported from 10 states- Lagos (53), Rivers (22), Akwa Ibom (12), Kaduna (12), Ondo (6), Osun (3), FCT (2), Jigawa(1), Nasarawa (1) and Kano (1). The southeast Nigeria put together with a population of approximately 22million people has recorded 9414 cases in total, 8783 discharged and 138 deaths (NCDC, 2021). This is in spite of the absence of vaccine intervention as well as virtually free movement and socioeconomic activities in all ramifications. Since the announcement of the first and second waves of covid-19 pandemic, local markets are densely populated on daily basis, public transport buses are filled to the brim, religious Academia Letters, July 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Samuel Okafor, samuel.okafor.pg76550@unn.edu.ng Citation: Okafor, S. (2021). Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria. Academia Letters, Article 2164. https://doi.org/10.20935/AL2164. 3 gatherings are filled with people ignoring social distance, there is a continuous inter city and state movements with the southeast Nigeria and between the region and other regions of the country. All non pharmaceutical precautionary measures instructed by the government and the international agencies are jettisoned among the population due to poor management as well as government nonchalant attitude towards the pandemic. Although a study with a number of health and public institutions have pointed out the incongruity between what is projected to the global community and the realities of covid-19 in Nigeria (Okafor forthcoming), the situation in southeast Nigeria and possibly other parts of Nigeria and Africa, negates the global synergy of covid-19 infection across homogenous and heterogeneous populations and possibly re-project the possibility of natural herd immunity in action against the covid-19 pandemic in this part of the world. This is in view of the deadly nature of the pathogen as has been observed in America, Europe, Asia, Latin America as well as some parts of Africa (CDC, 2021; John Hopkins Centre, 2021; The Royal Society, 2020; Harmaratne et al., 2020; Li et al., 2020). References Amzat, J., Aminu, K., Kolo, V. I., Akinyele, A. A., Ogundairo, J. A. & Danjibo, M. C. (2020). Coronavirus outbreak in Nigeria: Burden and socio-medical response during the first 100 days International Journal of Infectious Diseases 98 (2020) 218–224 Aschwanden, C. (2020). The false promise of herd immunity: Why proposals embraced by Donald Trump’s administration and others could bring “untold death and suffering”. Nature 587 (5) 26-28. Clemente-Suárez, V. J., Hormeño-Holgado, A., Jiménez, M, Benitez-Agudelo, J. C., NavarroJiménez, E, Perez-Palencia, N., Maestre-Serrano, R., Laborde-Cárdenas, C. C. & TorneroAguilera, J. C. (2020). Dynamics of Population Immunity Due to the Herd Effect in the COVID-19 Pandemic Vaccines 2020, 8, 236; doi:10.3390/vaccines8020236 Fine, P., Eames, K. & Heymann, D. L. (2011) “Herd Immunity”: A Rough Guide. Vaccines CID 52 (1) 911-916. Flaxman, S., Mishra, S., Gandy, A., Juliette, H., Unwin, T., Thomas A. M, Coupland, H., Whittaker, C., Zhu, H. Berah, T. Eaton, J. W. Monod, M., Imperial College COVID- 19 Response Team, Ghani, A. C., Donnelly, C. A., Riley, S., Vollmer, M. A. C, Ferguson, N. M., Okell, L. C. & Bhatt, S. (2020). Estimating the effects of non- pharmaceutical interventions on COVID-19 in Europe. Nature 584, 257–261. https://doi.org/10.1038/ s41586-020-2405-7 Academia Letters, July 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Samuel Okafor, samuel.okafor.pg76550@unn.edu.ng Citation: Okafor, S. (2021). Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria. Academia Letters, Article 2164. https://doi.org/10.20935/AL2164. 4 Harmaratne, S., Sudaraka, S., Abeyagunawardena, I., Manchanayake, K., Kothalawala, M. & Gunathunga, W. (2020). Estimation of the basic reproduction number (R0) for the novel coronavirus disease in Sri Lanka. Virol J 17, 144 (2020). https://doi.org/10.1186/s12985020-01411-0 Honigsbaum, M. (2009). Historical keyword Pandemic. The Lancet, 373. Jacob John T, Samuel R (2000). Herd immunity and herd effect: New insights and definitions. Eur J Epidemiol 16: 601-606. Jones, D. & Helmreich, F (2020). The art of medicine A history of herd immunity. The Lancet, 396,810-811 Kantner, M., Koprucki, T. (2020). Beyond just “flattening the curve”: Optimal control of epidemics with purely non-pharmaceutical interventions. J.Math.Industry 10, 23 (2020). https://doi.org/10.1186/s13362-020-00091-3 Korppi, M. (2018). Universal pneumococcal vaccination provides marked indirect beneficial effects through herd immunity. Acta Paediatr. 2018, 107, 1488–1489. Li, Y., Wang, LW., Peng, ZH. & Shen, H. B. (2019). Basic reproduction number and predicted trends of coronavirus disease 2019 epidemic in the mainland of China. Infect Dis Poverty 9, 94 (2020). https://doi.org/10.1186/s40249-020-00704-4 Liu, Y., Morgenstern, C., Kelly, J., Lowe, R., CMMID COVID-19 Working Group & Mark Jit (2021). The impact of non-pharmaceutical interventions on SARS-CoV-2 transmission across 130 countries and territories. BMC Med 19, 40 (2021). https://doi.org/10.1186/ s12916-020-01872-8 Metcalf, C. J. Ferrari, E. M., Graham, A.L. & Grenfell, B. T. (2015). Understanding herd immunity. Trends in Immunology, 36 (12), 753-735. Neil, M. F., Daniel, L., Gemma Nedjati-Gilani et al. (2020). Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand. Imperial College London, doi: https://doi.org/10.25561/77482. Prajapati S. & Narasimha K.G.V. (2020). Assumption of Herd Immunity against COVID-19: A plausibility and hope or a terrible thought in modern-day to save the life. J Infect Dis Epidemiol 6:147. doi. org/10.23937/2474-3658/1510147 Smith, P. G (2010). Concepts of herd protection and immunity. Procedia in Vaccinology (2) Academia Letters, July 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Samuel Okafor, samuel.okafor.pg76550@unn.edu.ng Citation: Okafor, S. (2021). Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria. Academia Letters, Article 2164. https://doi.org/10.20935/AL2164. 5 134–139 Topley, W. W. C & Wilson, G. S. (1923). The spread of bacterial infection: the problem of herd immunity. J Hyg, 21:243–9. WHO (2019). Non-pharmaceutical public health measures for mitigating the risk and impact of epidemic and pandemic influenza. Hong Kong: World Health Organization Yanga, Q., Xiaob, X, Gua, X., Liang, D., Caoa, T., Moua, J., Huanga, C. Chen, L. & Liu, J. (2021). Surveillance of common respiratory infections during the COVID-19 pandemic demonstrates the preventive efficacy of non-pharmaceutical interventions International Journal of Infectious Diseases 105 (2021) 442–447 Academia Letters, July 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Samuel Okafor, samuel.okafor.pg76550@unn.edu.ng Citation: Okafor, S. (2021). Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria. Academia Letters, Article 2164. https://doi.org/10.20935/AL2164. 6
ACADEMIA Letters Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria Samuel Okafor Over many centuries of human existence, the spread of disease has taken turns in different dimensions and has informed different approaches in managing same (Honigsbaum, 2009; Jones & Helmreich, 2020). While level of scientific advancement informs the approaches to the out breaking diseases, political activity and passivity contributes also, to the direction and magnitude of the approach. Central to whatever effort made in reaction to the outbreak of any disease, is to protect the population involved via population immunity. While the concept of immunity itself move from individual to population immunity (Metcalf, Ferrari, Graham & Grenfell, 2015), the realization of the concept is dependent on the spreading capacity or reproductive rate of the pathogen/virus as well as the fatality rate (Prajapati & Narasimha, 2020; Harmaratne et al., 2020; Li et al., 2020). Population immunity otherwise known as herd immunity is pursued and realized through the different clinical cum pharmaceutical as well as non pharmaceutical interventions (Smith, 2010; Aschwanden, 2020; Fine, Eames & Heymann, 2011). Specifically, population/herd immunity happens when a virus can’t spread because it keeps encountering people who are protected against infection. Once a sufficient proportion of the population is no longer susceptible, any new outbreak peters out (Aschwanden, 2020; Clemente-Suárez et al, 2020). A number of scholars have argued about the plausibility of the concept of herd immunity whether by clinical cum pharmaceutical intervention or by non pharmaceutical intervention (NPI), with major focus on the operationalization and measurability of the concept with a uniform protocol across the globe as well as across the heterogeneous and homogenous populations (Jacob & Samuel, 2000; Metcalf, Ferrari, Graham & Grenfell, 2015; The Royal Society, 2020). While herd/population immunity by clinical/pharmaceutical intervention has been argued for by many scholars with substantive evidences (Prajapati & Narasimha, 2020; Academia Letters, July 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Samuel Okafor, samuel.okafor.pg76550@unn.edu.ng Citation: Okafor, S. (2021). Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria. Academia Letters, Article 2164. https://doi.org/10.20935/AL2164. 1 Harmaratne et al., 2020; Li et al., 2020; Jones & Helmreich, 2020), herd/population immunity by non pharmaceutical intervention (NPI) has been equally projected as a reality among a helpless population in certain settings (Jones & Helmreich, 2020; Metcalf, Ferrari, Graham & Grenfell, 2015). Among other approaches, natural herd immunity as part of NPI, which allowed the spread of an infection to elapse with counter infection as well as unsusceptible members of the population, has been scarcely given attention to, across generations with history of epidemic and pandemics. While some scholars see natural immunity as intellectual venture full of spurious relationships of variables and as such, with complex and complicated explanations (The Royal Society, 2020; Jacob & Samuel, 2020), other scholars view natural immunity as not plausible and as such, unworthy of intellectual attention (Aschwanden, 2020). However, research venture is an ongoing process in every discipline with discoveries, counter discoveries and advanced discoveries as the case may be in different historical epochs. As a matter of fact, the case of CoViD-19 pandemic has brought to the limelight, the natural herd immunity phenomenon in focus, as evidences from different parts of the globe have defied the argument in favour of clinical/pharmaceutical intervention in pandemic crises. For instance, a number of projections have been made concerning African nations as well as other developing nations across the globe in the absence of vaccine; however, most of these nations did not fall within the projected figures and timeframe in the absence of vaccine to curtail the pandemic. Nigeria as one of the developing nations in Africa included in the number of projections about the spread of CoViD-19 pandemic, in the absence of vaccine, did not fall into the projection figure and framework following the present realities. This can be observed in the number of cases recorded till date. Nonetheless, the southeast Nigeria with dense population both in the urban and the rural communities, and complex socioeconomic activities before, during and after CoViD-19 lockdown, did not show any sign of the pandemic as was projected from different quarters about Nigeria. CoViD-19 Pandemic First and Second Waves in Southeast Nigeria and the Question of Natural Herd Immunity Basically in the principle of herd immunity, when a pathogen invades unexposed population, there is expectation of reproduction of the infection through the index case, producing a reproduction rate (R0) of varying degrees such that, there is a possibility of either increasing the infection in the population or phasing out the presence of the pathogen from the population that is, if R0 > 1 infection spreads; if R0 ≤ 1, infection dies out (The Royal Society, 2020). While this has been viewed as possible with the help of vaccine (Metcalf, Ferrari, Graham Academia Letters, July 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Samuel Okafor, samuel.okafor.pg76550@unn.edu.ng Citation: Okafor, S. (2021). Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria. Academia Letters, Article 2164. https://doi.org/10.20935/AL2164. 2 & Grenfell, 2015; Korppi, 2018), it has been also projected as possible through non pharmaceutical interventions (NPI) (Kantner & Koprucki, 2020; WHO, 2019; Neil et al, 2020), of which in difficult experience where the scientific prowess of a generation cannot counteract the spread of a pathogen, the population were left to the mercy of the infection and counter infection by the pathogen. From the moment in history when the concept of herd immunity entered into epidemiological literature (see Topley, Wilson, 1923) to the present, the application of the NPI ie the natural herd immunity dimension of the concept has been fairly observed in some period and places in the faces of epidemics and pandemics (Flaxman et al, 2020; Liu et al, 2021). While in the past, the application of natural herd immunity has been seen in the community of scientists and researchers as the by-product of unprogressive scientific effort in mitigating the spread of a pathogen, in the present historical epoch, with the current scientific prowess of this generation, practicing natural herd immunity is more or less seen as a suicide policy especially in the case of faceless virus like CoViD-19 (Aschwanden, 2020). In the wake of current CoViD-19 pandemic, a number of nations such as United Kingdom, America, Sweden, Brazil, Nigeria, etc. have voluntarily and involuntarily applied the concept of natural herd immunity ostensibly to buy time for the development of vaccine (Aschwanden, 2020; Yanga et al, 2020; Flaxman et al., 2020). While in some of these nations, this appeared as a policy statement, in others, it was covertly observed but obtrusively visible on the rate of infections observed (Flaxman et al, 2020). In the case of Nigeria and southeast Nigeria in particular, the experience of the population from statistical revelation and scholarly observation (Okafor forthcoming) aptly demonstrated the natural herd immunity in action. The spread of novel Corona Virus Disease (COVID-19) in Nigeria has been observed as a reality since the first index case in February 2020 triggering, public policy response from the government of Nigeria (Amzat, Aminu, Kolo, Akinyele, Ogundairo & Danjibo, 2020). Currently, the spread of the virus can still be observed but rather in a very slower rate. On the 26th of March 2021, 113 new confirmed cases and 3 deaths were recorded in Nigeria. Till date, 162388 cases have been confirmed, 149986 cases have been discharged and 2039 deaths have been recorded in 36 states and the Federal Capital Territory. The 113 new cases are reported from 10 states- Lagos (53), Rivers (22), Akwa Ibom (12), Kaduna (12), Ondo (6), Osun (3), FCT (2), Jigawa(1), Nasarawa (1) and Kano (1). The southeast Nigeria put together with a population of approximately 22million people has recorded 9414 cases in total, 8783 discharged and 138 deaths (NCDC, 2021). This is in spite of the absence of vaccine intervention as well as virtually free movement and socioeconomic activities in all ramifications. Since the announcement of the first and second waves of covid-19 pandemic, local markets are densely populated on daily basis, public transport buses are filled to the brim, religious Academia Letters, July 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Samuel Okafor, samuel.okafor.pg76550@unn.edu.ng Citation: Okafor, S. (2021). Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria. Academia Letters, Article 2164. https://doi.org/10.20935/AL2164. 3 gatherings are filled with people ignoring social distance, there is a continuous inter city and state movements with the southeast Nigeria and between the region and other regions of the country. All non pharmaceutical precautionary measures instructed by the government and the international agencies are jettisoned among the population due to poor management as well as government nonchalant attitude towards the pandemic. Although a study with a number of health and public institutions have pointed out the incongruity between what is projected to the global community and the realities of covid-19 in Nigeria (Okafor forthcoming), the situation in southeast Nigeria and possibly other parts of Nigeria and Africa, negates the global synergy of covid-19 infection across homogenous and heterogeneous populations and possibly re-project the possibility of natural herd immunity in action against the covid-19 pandemic in this part of the world. This is in view of the deadly nature of the pathogen as has been observed in America, Europe, Asia, Latin America as well as some parts of Africa (CDC, 2021; John Hopkins Centre, 2021; The Royal Society, 2020; Harmaratne et al., 2020; Li et al., 2020). References Amzat, J., Aminu, K., Kolo, V. I., Akinyele, A. A., Ogundairo, J. A. & Danjibo, M. C. (2020). Coronavirus outbreak in Nigeria: Burden and socio-medical response during the first 100 days International Journal of Infectious Diseases 98 (2020) 218–224 Aschwanden, C. (2020). The false promise of herd immunity: Why proposals embraced by Donald Trump’s administration and others could bring “untold death and suffering”. Nature 587 (5) 26-28. Clemente-Suárez, V. J., Hormeño-Holgado, A., Jiménez, M, Benitez-Agudelo, J. C., NavarroJiménez, E, Perez-Palencia, N., Maestre-Serrano, R., Laborde-Cárdenas, C. C. & TorneroAguilera, J. C. (2020). Dynamics of Population Immunity Due to the Herd Effect in the COVID-19 Pandemic Vaccines 2020, 8, 236; doi:10.3390/vaccines8020236 Fine, P., Eames, K. & Heymann, D. L. (2011) “Herd Immunity”: A Rough Guide. Vaccines CID 52 (1) 911-916. Flaxman, S., Mishra, S., Gandy, A., Juliette, H., Unwin, T., Thomas A. M, Coupland, H., Whittaker, C., Zhu, H. Berah, T. Eaton, J. W. Monod, M., Imperial College COVID- 19 Response Team, Ghani, A. C., Donnelly, C. A., Riley, S., Vollmer, M. A. C, Ferguson, N. M., Okell, L. C. & Bhatt, S. (2020). Estimating the effects of non- pharmaceutical interventions on COVID-19 in Europe. Nature 584, 257–261. https://doi.org/10.1038/ s41586-020-2405-7 Academia Letters, July 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Samuel Okafor, samuel.okafor.pg76550@unn.edu.ng Citation: Okafor, S. (2021). Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria. Academia Letters, Article 2164. https://doi.org/10.20935/AL2164. 4 Harmaratne, S., Sudaraka, S., Abeyagunawardena, I., Manchanayake, K., Kothalawala, M. & Gunathunga, W. (2020). Estimation of the basic reproduction number (R0) for the novel coronavirus disease in Sri Lanka. Virol J 17, 144 (2020). https://doi.org/10.1186/s12985020-01411-0 Honigsbaum, M. (2009). Historical keyword Pandemic. The Lancet, 373. Jacob John T, Samuel R (2000). Herd immunity and herd effect: New insights and definitions. Eur J Epidemiol 16: 601-606. Jones, D. & Helmreich, F (2020). The art of medicine A history of herd immunity. The Lancet, 396,810-811 Kantner, M., Koprucki, T. (2020). Beyond just “flattening the curve”: Optimal control of epidemics with purely non-pharmaceutical interventions. J.Math.Industry 10, 23 (2020). https://doi.org/10.1186/s13362-020-00091-3 Korppi, M. (2018). Universal pneumococcal vaccination provides marked indirect beneficial effects through herd immunity. Acta Paediatr. 2018, 107, 1488–1489. Li, Y., Wang, LW., Peng, ZH. & Shen, H. B. (2019). Basic reproduction number and predicted trends of coronavirus disease 2019 epidemic in the mainland of China. Infect Dis Poverty 9, 94 (2020). https://doi.org/10.1186/s40249-020-00704-4 Liu, Y., Morgenstern, C., Kelly, J., Lowe, R., CMMID COVID-19 Working Group & Mark Jit (2021). The impact of non-pharmaceutical interventions on SARS-CoV-2 transmission across 130 countries and territories. BMC Med 19, 40 (2021). https://doi.org/10.1186/ s12916-020-01872-8 Metcalf, C. J. Ferrari, E. M., Graham, A.L. & Grenfell, B. T. (2015). Understanding herd immunity. Trends in Immunology, 36 (12), 753-735. Neil, M. F., Daniel, L., Gemma Nedjati-Gilani et al. (2020). Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand. Imperial College London, doi: https://doi.org/10.25561/77482. Prajapati S. & Narasimha K.G.V. (2020). Assumption of Herd Immunity against COVID-19: A plausibility and hope or a terrible thought in modern-day to save the life. J Infect Dis Epidemiol 6:147. doi. org/10.23937/2474-3658/1510147 Smith, P. G (2010). Concepts of herd protection and immunity. Procedia in Vaccinology (2) Academia Letters, July 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Samuel Okafor, samuel.okafor.pg76550@unn.edu.ng Citation: Okafor, S. (2021). Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria. Academia Letters, Article 2164. https://doi.org/10.20935/AL2164. 5 134–139 Topley, W. W. C & Wilson, G. S. (1923). The spread of bacterial infection: the problem of herd immunity. J Hyg, 21:243–9. WHO (2019). Non-pharmaceutical public health measures for mitigating the risk and impact of epidemic and pandemic influenza. Hong Kong: World Health Organization Yanga, Q., Xiaob, X, Gua, X., Liang, D., Caoa, T., Moua, J., Huanga, C. Chen, L. & Liu, J. (2021). Surveillance of common respiratory infections during the COVID-19 pandemic demonstrates the preventive efficacy of non-pharmaceutical interventions International Journal of Infectious Diseases 105 (2021) 442–447 Academia Letters, July 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Samuel Okafor, samuel.okafor.pg76550@unn.edu.ng Citation: Okafor, S. (2021). Natural Herd Immunity and CoViD-19 Pandemic: A Peripheral Observation in Southeast Nigeria. Academia Letters, Article 2164. https://doi.org/10.20935/AL2164. 6